open reel - Computer Definition

A reel of magnetic tape. It typically refers to half-inch open reels that still remain in the archives of many data libraries. In the 1950s, before the 8-bit byte, 7-track tapes (seven parallel tracks) were used to accommodate a 6-bit character plus parity. Starting in the 1960s, 9-track tapes were used to support the byte. See half-inch tape and magnetic tape.

The Venerable Open Reel

Practically extinct today, open reels were the common means of computer storage from the 1950s to the 1970s. The earlier drives required manual threading of the tape onto the empty takeup reel.